Effect of land-use change on soil fertility characteristics within water-stable aggregates of two cultivated soils in northern Iran

Forest and pastureland soils in highland of northern Iran are being seriously degraded and destructed due to extensive agricultural activities. These land use changes are usually accompanied by decreasing in concentrations of soil organic carbon and nutrients and also deterioration of soil structure in these regions. However, studies on concentration of nutrients and carbohydrates in soils suggest that the location of nutrients within aggregates of each size should be determined. This study was to evaluate the nutrient elements and carbohydrate distributions within water-stable aggregates (WSA) of virgin forest and pasture lands under different land uses in Alborz maintain range, northern Iran. In September 2006, soil samples were collected from depths of 0–20 cm in Typic Haploxerolls soils. The overall pattern indicated that the mean weight diameter (MWD) and WSA were greater in the virgin pasture and forest soils compared with the adjacent cultivated (ex-forest and ex-pasture) soils and aggregates of >1.0 mm size were dominant in the virgin soils, whereas the cultivated soils comprised aggregates of the size ≤0.5 mm. Distribution of organic carbon, nitrogen, phosphorus and carbohydrates within the WSA showed preferential enrichment of these parameters in the macroaggregate fraction (4.75–1.0 mm) for the virgin soils and microaggregate fraction (>0.25 mm) for the exposed soils. Cultivation decreased the concentration of carbohydrates by 23.6% and 20.6% in ex-forest and ex-pasture lands, respectively. Average distribution of total exchangeable bases within WSA showed that the cultivation of forest and pasture soils significantly led to reduce in these nutrient in the 4.75–2.0 mm fraction and increase in concentration of these exchangeable cations in <0.25 mm fractions. In general, results indicated that cultivation significantly led to 71% and 6% reductions in total exchangeable bases within the 4.75–2.0 and <0.25 mm aggregate fraction, respectively, for virgin soil. Since smaller aggregates are preferentially removed by erosion, this study emphasizes the need for sustainable soil management practices that they will minimize nutrient loss when forest or pastures lands are converted to croplands.     

河南省土地利用变化特征及其空间格局

[目的]通过分析河南省2011~2016年土地利用变化特征和空间格局状况,以期为日后河南省合理开发、利用土地资源提供一定的理论指导。[方法]基于河南省土地变化特征,通过马尔科夫模型对河南省2011~2016年土地变化特征进行分析,从多个角度揭示该地区土地利用结构变化情况,并对河南省土地空间利用变化进行评价。[结果]河南省建设用地增加幅度最大,耕地、水域用地有不同程度的减少。土地空间变换主要表现为耕地和林地、水域用地、建设用地等土地类型之间的变换。由土地利用综合区可知,不同土地类型转换过程中,草地是转换比率最小的类型。[结论]河南省的各类土地利用之间的矛盾日益激烈,直接或间接地影响社会经济制度、土地政策和土地管理,因此,有必要加强开展土地资源管理和规划、保护生态环境等方面的工作。     

Evaluating the sustainability of the gray-whale-watching industry along the pacific coast of North America

This paper reports on the first study to critically examine the sustainability of whale-watching practices along the entire migratory range of a pelagic baleen whale species, the gray whale (Eschrichtius robustus). Commercial boat-based whale-watching operations along the west coast of North America were observed for sustainable practices. Data recorded aboard whale-watching vessels and collected via an online survey were integrated into the Lean Six Sigma quality-improvement tool, in order to review business processes and identify where inefficiency or ineffectiveness exists in specific phases within a process. Whale-watching practices were analyzed using this method for 24 whale-watching companies operating in Canada, the United States and Mexico. The results show a high level of variation in management regimes, and operator non-compliance with guidelines, and highlight avenues to eliminate, revise or reduce inefficiency, and improve practices in the interests of high-quality and sustainable operations. We recommend more specific and operational guidelines that allow operators to focus on high compliance with the most critical aspects of their business operation in order to build the sustainability of commercial tourist interactions with gray whales in their migratory range.     

新型靶场全空域全数字相控阵测控系统设计

针对后续靶场多发齐射等新型试验任务的测控保障需求，提出了基于全空域覆盖多频段综合孔径天线阵列、分布式数据采集与传输、多功能通用“资源池”为基础的新一代靶场多功能综合测控系统。针对靶场遥测常用的S频段和安控常用的P频段，给出了双频段共阵面全空域覆盖相控阵的具体实现方式，并仿真分析了核心指标。仿真结果表明，全空域增益波动在1 dB内，第一副瓣电平均小于-13.0 dB。此外，该系统架构具有可扩展性。     

人民陪审员制度的系统完善--学习《关于完善人民陪审员制度的决定》

全国人大常委会最近通过的《关于完善人民陪审员制度的决定》对在我国已经施行多年的人民陪审制度在陪审案件的范围、人民陪审员的任职条件、选拔方式和明确人民陪审员的权利与职责等方面进行了系统的完善。     

高职全方位校企合作模式的实证性研究——以广东女子职业技术学院旅游管理专业为例

全方位校企合作模式是当前适合高职院校与企业合作办学的较为完善的一种模式。该模式通过校企双方投入必须的人财物,负有相应的教育管理责任,合作提高教育教学质量,实现校企双方共同发展的目标。     

管理会计的射程与边界

管理会计的射程与边界即管理会计学科研究的范围。射程问题是由管理会计功能引发的发展问题。边界问题主要是由学科之间的关系引发的联系问题,可从横向和纵向两个角度考察。横向边界研究涉及管理会计学与会计学内部各学科及其与管理学、经济学之间的关系。纵向边界研究包含管理会计学科理论层面的扩展,以及基于供应链的管理会计发展。本文指出：随着管理会计工具的不断创新与整合,管理会计的发展已经进入了“价值创造的管理会计”阶段,具有“经济计算和信号传递”以及“生产、技术导向和组织结构”两种系列功能。应该通过研究管理会计学科的内外部关系,来有效规范和控制管理会计的边界,同时要针对经营控制逆反性,寻求平衡与发展。     

High-low range in GARCH models of stock return volatility

We suggest a simple and general way to improve the GARCH volatility models using the intraday range between the highest and the lowest price to proxy volatility. We illustrate the method by modifying a GARCH(1,1) model to a range-GARCH(1,1) model. Our empirical analysis conducted on stocks, stock indices and simulated data shows that the range-GARCH(1,1) model performs significantly better than the standard GARCH(1,1) model both in terms of in-sample fit and out-of-sample forecasting ability.     

A conditional autoregressive range model with gamma distribution for financial volatility modelling

The commonly used conditional autoregressive range model with Weibull distribution (henceforth WCARR) suffers from serious inlier problem. We conjecture that this problem is due to a misspecified distribution to the disturbance, and propose a conditional autoregressive range model with gamma distribution (henceforth GCARR) to model the volatility of financial assets. In this paper, we first discuss the theoretical properties of the GCARR model and then compare its empirical performance with the WCARR. Empirical studies are performed on a broad set of stock indices in different countries over different time horizons. Consistent with the conjecture, we find that the GCARR model can reduce not only the inlier problem but also the outlier problem of the WCARR model. The results indicate that our GCARR model describes the dynamics of the range-based volatility better than the WCARR model and thus serves as a better benchmark.     

铁路运输危险气体泄漏扩散模拟分析

针对铁路运输危险气体泄漏事故的特点,文章以高斯烟羽模型为基础,借助Matlab编程对不同条件下(不同风速、不同大气稳定条件和多泄漏源等)的铁路危险性气体扩散范围进行模拟分析,实现了危险性气体扩散的直观图形表示和伤害分区的划分,为指导铁路运输紧急救援提供一定的指导作用。